These are not competing products so much as two places a pension can live. A workplace pension is arranged by an employer, who must contribute to it. A SIPP is arranged by you, and nobody contributes unless you or your company do. That single difference decides most cases before any comparison of charges or investment choice begins.
The employer contribution is usually decisive
GOV.UK sets out that under automatic enrolment an employer must pay into a workplace pension for eligible staff. That contribution is money that exists only inside the workplace scheme. Opting out to fund a SIPP instead gives it up, and no difference in platform charges or fund choice recovers a contribution that was never made. For an employee, the sensible question is almost never whether to swap one for the other but whether to run a SIPP alongside.
Where the SIPP genuinely wins
Investment freedom and consolidation. A workplace scheme offers a limited menu built to suit everybody, and most members stay in the default fund. A SIPP opens the choice up, and a full SIPP can hold assets a workplace scheme will never touch, including commercial property. It is also the natural home for old pensions from previous employers, which otherwise sit in several places accruing several sets of charges. For a company director without an employer scheme in any meaningful sense, the SIPP is often the main arrangement rather than a supplement.
Holding both is the normal answer
Nothing prevents it. There is no limit on the number of pensions, and contributions to all of them share one annual allowance, which GOV.UK states is 60,000 pounds a year and counts employer contributions as well as your own. The usual arrangement is to take the workplace pension for the employer money and use a SIPP for anything beyond it, which captures the contribution and the flexibility rather than choosing between them.
What this page does not settle
Whether to transfer an existing workplace pension into a SIPP is a different question from where new contributions go, and it can involve giving up guarantees or protected benefits. This site does not advise on transfers, which is a regulated activity, and it does not recommend a provider. Where a transfer needs a recommendation, the enquiry goes to an authorised firm.
Questions people ask about SIPP vs workplace pension
Should I opt out of my workplace pension for a SIPP?
Rarely, because opting out usually forfeits the employer contribution, and that is money available nowhere else. Lower charges or wider fund choice in a SIPP do not compensate for a contribution that is never made. Running both is the more common answer.
Can I have a SIPP and a workplace pension together?
Yes. There is no limit on how many pensions you hold. Contributions across all of them share one annual allowance, which GOV.UK states is 60,000 pounds a year including what your employer pays in.
Is a SIPP better for a company director?
Often it is the main arrangement, because a director may have no meaningful employer scheme and can have the company contribute directly to a SIPP. It also permits holding assets such as commercial premises, which a workplace scheme will not.
Should I move an old workplace pension into my SIPP?
It can simplify things and reduce duplicated charges, but older pensions sometimes carry guaranteed rates or protected benefits lost on transfer. Ask the existing provider in writing what would be given up before moving anything.