The guarantee, for individual pensions/drawdown and onshore investment bond businesses, should help advisers transition to the new charging structure of RDR, says Aegon.
The only exception to the guarantee is for unit-linked guarantees and offshore investment bonds.
The Aegon Secure Trustee Investment plan will have a commission quotation period of two months and all other unit-linked Aegon UK and Aegon Ireland products will have a commission quotation period of one month. For offshore products, the firm will honour a commission quote until 5 April 2013, the end of the current tax year.

For corporate pension business, commission quotes will be guaranteed from six months after the completion of the advice.
Richard Dallas, Aegon's marketing and transformation director, said: "Anything that would disrupt the provision of advice as we move into 2013 would be bad for customers. So we'll be providing a commission guarantee where the advice process has been completed by 30 December 2012, enabling advisers to honour the commitments they have made to their clients.
"At Aegon we already offer adviser charging through our platform proposition (Aegon Retirement Choices) and will offer adviser and/or consultancy charging on our soon to launch corporate platform solution."