Re: How many decades ?
"When can I refuse to comply with a request for erasure?
You can refuse to comply with a request for erasure where the personal data is processed for the following reasons:
•to exercise the right of freedom of expression and information;
•to comply with a legal obligation or for the performance of a public interest task or exercise of official authority;
•for public health purposes in the public interest;
•archiving purposes in the public interest, scientific research historical research or statistical purposes; or
•the exercise or defence of legal claims."
Accounts records being legal requirement comes under 2? So looks like you'd need system to hold requests until the right period had expired.