This story is based on a small little idea that I got from reading order stories but none of them explored this idea like I have. Please enjoy!
The Golden Trio, after giving Snape's memories to Professor McGonagall, gathered with the remaining Weasleys in the infirmary to mourn the death of Remus, Tonks, Percy and all their other friends while waiting to hear news of Fred. Fred was in the hospital recovering from his injuries. Percy used his own body to shield his brother from the falling wall. Snape's body had been recovered from the Shrieking Shack by McGonagall after she and Harry reviewed the memories in a pensive. Snape was secluded in a private room in the back of the infirmary in a coma that no one was sure that he would awake from. As far as the healers could make out, he had been giving himself small doses of an experimental potion mixed with Nagini's venom to make himself immune to her bite. His body was recovering from the injury to his neck and the blood loss. After Fred awoke, Bill and Charlie took the younger kids home while Arthur, Molly, and George stayed with Fred. The kids all showered and went to bed without even bothering to eat. Fleur joined Bill and Charlie at the Burrow to watch over everyone until the rest of the family could return home.
The Goblins received word that Voldemort had been defeated as the Goblins assigned to watch the battle reported back to the bank. Newly-appointed Head Goblin Ragnok called an immediate meeting of the board and listened to the details and then dismissed the Goblins. He turned to the other board members and asked for their recommendations. As the board members discussed the various changes from the corrupt Voldemort-controlled ministry that needed to be undone, one of the oldest board members, Teartooth, remained silent. Ragnok turned to Teartooth and asked him for his opinion. Teartooth began to speak and started reciting all of the past Wizarding wars and the consequences for the bank. In each and every case, almost immediately after each war, the Wizards found some way to put blame on the Goblins and its bank in order to financially penalize the Goblins and refill the ministry's coffers. Ragnok asked Teartooth what he thought that they should do. The old Goblin replied that they should make a preemptive strike against the wizards to make the Goblins look good and the ministry look bad. He quoted several lines from the most recent Goblin-Wizard treaty (pre-Voldemort, of course) referring to the inheritance of heirs of the war dead, legitimate or illegitimate. Ragnok reminded Teartooth that the Goblins were strictly prohibited from disclosing heir status unless the request came directly from an heir. Teartooth explained his plan to release the information using the Wizards themselves, specifically one bushy-haired, know-it-all, war heroine who thrived on "tilting at windmills", especially against purebloods. The incident with the breaking in Gringotts and the theft of the dragon would provide the bank the opportunity to set the wheels in motion and not violate the treaty. Ragnok knew that Teartooth had a sharp, legal mind and knew every treaty and law regarding Goblin/Wizard relations. The board members quickly voted on Teartooth's recommendation and appointed Teartooth to handle the matter while the other department went into action reversing legislation created by Voldemort's Ministry.
The next morning, the golden trio woke to the smell of breakfast cooking. They went downstairs found the family eating and laughing. A pale Fred was sitting next to a jubilant George while Molly cooked over the stove. Ginny was helping her mother by putting plates on the table. As they ate breakfast, Molly explained that Arthur and Charlie had gone to the ministry to find out what was going on. Bill and Fleur were still asleep upstairs in Bill and Charlie's old room. As a delivery owl arrived with the morning edition of the Daily Prophet, a Gringotts' owl entered as landed in front of Hermione and immediately stuck its foot out. Everyone was nervous about the owl until Hermione waved her wand and checked out the letter magically. Satisfied that nothing was out of the ordinary with it, she removed the letter from the owl's leg and it immediately flew away.
Reading it quickly, she showed the letter to the others. The letter politely invited her to Gringotts to discuss her financial responsibility for her share of the damages to the bank caused by "unauthorized removal of Gringotts' property from the bank premises". Soon afterward, two more owls appeared with similar letters for Harry and Ron. After Bill awoke at noon, they discussed the situation with him and he told them that the sooner they dealt with this, the less angry the Goblins would be. Bill offered to escort them to the bank and flooed them directly to the bank via a Wizard employee entrance beside the bank. Before they entered the bank through a rear entrance, they could hear the noise of the party-goers still celebrating in Diagon Alley. Bill took them through the bank to the main offices and stood in front of an imposing desk with a fierce Goblin teller who was working on stacks of paperwork.
The Goblin teller immediately dismissed Bill and herded the trio into a small conference room. Harry immediately spoke up and told the Goblin that he would take care of any financial responsibility through his vaults. The Goblin teller's smirk grew fiercer as he politely informed Harry that the Potter vaults were nearly empty of any gold or valuables. He presented Harry with pages of withdrawals from his parents' vaults by Dumbledore. Even before the deaths of James and Lily Potter, Dumbledore and his Order of the Phoenix removed much of the gold in the vaults. James had willingly liquidated many of the Potter family's valuables to help financially support Dumbledore. The little house at Godric's Hollow was the only piece of property left and it needed many repairs before it was even inhabitable. Only Harry's school fund had been protected. The Black family assets also suffered from their support of Voldemort. Only the house at Grimmauld Place remained, as it was still Walburga's home and under the Fidelius charm when she died.
The Goblin teller sneered at the teenagers and slid over an identical parchment to each one showing their share of the damages. The Goblin teller's sneer turned into a smirk as the three teens paled. He discretely pressed a button under the table and a much older Goblin entered the room with a stone box.
Teartooth glanced at the pale teens before nodding at the Goblin teller. The Goblin teller rose from the desk and left the room after bowing to Teartooth. Teartooth took his seat and faced the bewildered teens. He grimly explained to the teens that even though they were considered to be heroes by the Wizarding world, the Goblin nation would treat them exactly the same as all other witches and wizards. Since none of the teens had funds available in any currently owned vaults, one of the only three possible sources of additional funds to cover their fines would have to be provided by any friends or family would could afford to pay their debts. The trio looked at each other and each one shook their head at the others.
Teartooth sneered at the teens and suggested that they could also choose to work off the debts by working for Gringotts in their mines. After all, someone had to shovel all the dragon dung. Hermione raised the question of the third possibility and Teartooth leered and explained that if the trio wished that Gringotts could perform inheritance tests on them to see if they were the heirs of any existing unclaimed vaults and summarized several references to the most recent Wizard/Goblin treaty. Ron asked how this would affect him since his parents were living and he had several brothers who should inherit before him. Teartooth explained that only the first witch or wizard in a family who took the test could claim any previously frozen vaults and their contents. That witch or wizard could choose to share the contents of the vaults with their existing family if they wished. Hermione explained that she was a muggleborn and had no Wizarding ancestors. Teartooth explained that if by some possible chance she had squib ancestors then she too might be eligible to inherit vaults from lines that died out who had previously cast out their squib relations. The old Goblin explained that many squibs simply left home as teenagers and sought their fortunes in the muggle world. Any blood ancestor of a squib could restart their family line if no other wizard relations currently existed. Teartooth looked to Harry and pointed out that perhaps Lily Evans may not have been a muggleborn but squib-descended. Hermione asked why no one mentioned this to anyone before. Teartooth explained that the most current treaty prevented the Goblins from mentioning this except for the most extreme situations but that many of the pureblood Wizards in the Wizengamot who approved the treaty did not want to publicize it. Harry, Ron and Hermione looked at each other and silently agreed. Harry spoke for them all and asked to Goblin to perform the tests.
Teartooth opened the stone box that he brought into the conference room. He pulled out several pieces of thick parchment, a stone ritual knife, and a vial of potion. He placed a piece of parchment in front each of the teens. He instructed them to place 5 drops of blood on the center of the parchment. He motioned them show their palms and then slit each one. After the teens bled on their parchments, Teartooth poured 5 drops of potion into each of the blood stains and then waved the knife over their palms (which instantly closed the wounds with no scarring).
As the potion mixed with the blood on each parchment, words began to appear as a list of vaults began to appear of each parchment. Harry was not surprised to see the names Potter and Black appear but he did not expect the names Riddle, Slytherin, Peverell, Burke, Bagshot, or Moody. Hermione was equally shocked to see the names Dagworth-Granger, Rosier and Dolohov on hers. Ron stared at the name Yaxley on his parchment as if it would jump up and bite him. He then nudged Harry and showed him that the name Black was also listed. The three teens all looked to the Goblin who wore a look of smug satisfaction. Teartooth instructed the teens to tap on a name after the vault number for more information.
Hermione wearily tapped on the name Dolohov and a several sentences popped up under the Vault Number: "Antonin Dolohov, Senior sired Sarah Elaine Grayson who was the mother of Helen Sarah Peters who was the mother of Hermione Jane Granger." The trio stared at the parchment as Hermione sputtered and looked to Teartooth for an answer. The Goblin glanced at the parchment and sniped at the girl in exasperation. He explained that either Sarah Grayson was a squib who was cast out and ran away to the muggle world or the product of a wizard "playing" with a Muggle female and using an obliviate spell but forgetting or incorrectly using a contraceptive spell. Hermione then moved her ward to to the Rosier and tapped it with her wand and produced "Stephan Rosier sired Stephan Rosier Junior who changed his name to Steven Rosen when he joined the British Army at the age of 15 who later married and sired Joanna Louise Rosen who married Thomas Stanley Granger who sired Robert Drew Granger who sired Hermione Jane Granger." Hermione then tapped Dagworth-Granger and produced "Hector Dagworth-Granger sired Peter Dagworth-Granger who changed his name to Peter David Granger when he joined the Royal Navy at age 14 who later married and sired Daniel Hector Granger who sired Francis Henry Granger who sired Thomas Stanley Granger who sired Robert Drew Granger who sired Hermione Jane Granger."
Ron put on a brave face as he tapped the name Black on his parchment "Lysandra Black (née Yaxley) left a vault to her disowned daughter Cedrella after her marriage to Septimus Weasley which she declared separate from the main Black line. Cedrella Weasley sired Arthur Weasley who sired Ronald Bilius Weasley." Ron then tapped the name Yaxley and produced "Corban Yaxley was killed during the final battle and left no heirs to the Yaxley line. The Yaxley vault reverts to closest living blood relative Ronald Bilius Weasley."
Harry looked to his own parchment and tapped the name Moody and produced "Alastor Moody listed Harry James Potter as his magical heir as he had no other living relatives." Harry's eyes grew misty and Hermione and Ron grasped his hands. He gathered himself and tapped on the name Bagshot which listed "Bathilda Bagshot listed Harry James Potter as her magical heir as she had no other living relatives." He tapped on Burke and read "Caractacus Burke sired Margaret Mary Ferguson who was the mother of William John Evans who sired George Mack Evans who sired Lily Jasmine Evans who was the mother of Harry James Potter." He then tapped Peverell and saw "Peverell, as Harry James Potter is the last blood descendant to Peverell line through Ignotus Peverell as Cadmus Peverell's line ended with the death of Tom Marvolo Riddle and Antioch Peverell died without any heirs, all Peverell vaults revert to last living blood relation, Harry James Potter." Harry then tapped on Slytherin which showed "Salazar Slytherin's last living closest blood relative, Tom Marvolo Riddle died without any heir which causes the Slytherin Vaults to revert to the nearest living blood relative through the Peverell line to Harry James Potter." Harry also tapped on Riddle and read "Tom Marvolo Riddle died without any heirs. His vault reverts to his remaining living blood relative, Harry James Potter."
Teartooth gathered the parchments and placed them on a stone tablet on the desk. Almost immediately, the parchments glowed and copied themselves. He then placed the copies in a folder which flashed and within minutes several tellers entered the room and started handing out additional vault statements to the trio. Comparing statements, the three teens realized that each one of them had more than enough gold to cover any damages to the bank.
Hermione was the first to realize the implications of the inheritance tests and asked Teartooth why no one mentioned these tests to her or any other muggleborn before. Teartooth grinned a ghastly grin and explained that the most current goblin-wizard treaty specifically prevented goblins from telling any wizards (including muggleborns) about any unclaimed vaults but it did not prohibit any witches or wizards from asking for inheritance tests on their own.
Teartooth explained that, in the past, so-called muggleborns were offered testing whenever they first entered the bank. Some so-called purebloods became upset that so many long dormant vaults were being claimed by squib-descended relatives. He further explained that Gringotts wants inactive vaults reactivated because it generates more profit for the bank. During the last treaty negotiations, Purebloods included specific portions into the treaty to keep the squib-descendants from knowledge that threatened the Purebloods hold over the Wizarding world.
Hermione almost jumped from her seat when she realized what this could mean to other muggleborns while Ron strategized over this news and Harry continued to simply goggle at the names on his piece of parchment. Hermione asked Teartooth if they could pay their portions of the damages owed from their new vaults. He pressed a button on the desk for quill and ink to appear and handed them each a form to sign. Hermione read carefully over the similar forms and nodded for the boys to sign as she picked up the quill and signed her form. Once all the paperwork was completed the trio made appointments to return to the bank the next day to visit the new vaults and examine the contents for anything other than just gold.
The three teens found a relieved Bill in the lobby and quickly returned to the Burrow to stratigize. They decided that the best course of action was to send letters to all the friends in the DA to go to Gringotts and have their own inheritance test performed before letting the general public know. This would allow their friends to claim any possible vaults before the remaining purebloods tried to stop them and claim those vaults for themselves. They knew that if asked Luna would delay publicizing the news in the Quibbler until the remaining DA members could get to the bank.
Of course, what the trio found in their new vaults is an adventure for another story.